I get why the background is the way it is. twilight is on Celestia's side so they put her on the daytime side. but that would mean that the "great and powerful Trixie" would fight for Luna if there was a civil war between which princess would rule the kingdom, and she was introduced as a villain. this could mean that everypony that DOES'NT have the proper loyalties to Celestia are considered "bad ponies" and shunned by the rest of society. this would explain why she never got a stationary job, instead traveling all over the place like the wandering jew. she has to move quickly from one town to the next because if she stayed too long, ponies would find out her secret and banish her to the badlands.